Antti Haapala:
> However what I'd prefer here as the size of the type is important, to use `uint16_t` or typedef instead of just `unsigned short`, which is a statemeent that the value must be at least "2 bytes wide".

I'm not aware of a platform where sizeof(unsigned short) is not *exactly* 16-bits. At least, no platform supported by CPython.

Include/unicodeobject.h is quite explicit:

#if SIZEOF_SHORT == 2
typedef unsigned short Py_UCS2;
#else
#error "Could not find a proper typedef for Py_UCS2"
#endif

Maybe we should use a similar code in ceval.c?

#if SIZEOF_SHORT != 2
#  error "Could not find a proper type for 16-bit pointer"
#endif